Nilo® K

A Nickel-Iron-Cobalt, controlled expansion alloy containing 29% Nickel. Its coefficient of expansion (which decreases with rising temperature to the inflection point), matches the expansion rate of borosilicate glasses and alumina ceramics.

Nilo® K is also known as Kovar, Dilver, and Pernifer 2918.

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Key Features

Controlled coefficient of expansion (which decreases with rising temperature to the inflection point).
Matches the expansion rate of borosilicate glasses and alumina ceramics.

Typical Applications

Glass to metal seals in applications requiring high reliability or resistance to thermal shock, ie. high power transmitting valves

Chemical Composition

Element	Min %	Max %
Fe	53.00 nominal
Ni	29.00 nominal
Co	17.00 nominal
Mn	–	0.50
Si	–	0.20
C	–	0.04
Al	–	0.10
Mg	–	0.10
Zr	–	0.10
Ti	–	0.10
Cu	–	0.20
Cr	–	0.20
Mo	–	0.20

Alloy Details

Density	Melting Point	Inflection Point	Thermal Conductivity	Coefficient of Expansion
8.16 g/cm³	1450 °C	450 °C	16.7 W/m• °C	6.0 µm/m °C (20 – 100 °C) 4.6 – 5.2 µm/m °C (20 – 400 °C)
0.295 lb/in³	2640 °F	840 °F	116 btu•in/ft²•h °F	3.3 x 10^-6 in/in °F (70 – 212 °F) 2.6 – 2.9 x 10^-6 in/in °F (70 – 752 °F)

Heat treatment of finished parts

The Nilo alloys are usually supplied and used in the annealed condition (residual cold work distorts the coefficients of thermal expansion). Annealing times may vary due to section thickness. Oxidizing time and temperature to be selected depending on required oxide thickness.

	Type	Temperature	Time	Cooling
	Anneal	850 – 1000 °C (1560 – 1830 °F)	0.5 Hr	Air or water
To prepare for glass to metal sealing	Decarburization	900 – 1050 °C (1650 – 1920 °F)	1 Hr	Air or water
If a metal oxide interface is required (time and temperature depend on required oxide thickness)	Oxidize	600 – 1000 °C (1110 – 1830 °F)	1 Hr	Air